1. Field of the Invention
The present invention relates to an electric power source which is installed in a motor vehicle such as a hybrid vehicle, electric vehicle and fuel-cell vehicle to supply electric power to a motor for driving the vehicle, and also pertains to a welded state detection method for discriminating an electrically welded state of a contactor mounted to the power source.
2. Description of the Related Art
An electric power source for a motor vehicle connects positive-side and negative-side contactors respectively on its output side. The contactor is switched on or off by means of an ignition switch in the vehicle. When the ignition switch is turned on, the contactor is also switched on, so that a driving motor comes to be electrically supplied from the power source. When the ignition switch is turned off, the contactor is switched off, so that output power from the power source is separated from a loading side, thus avoiding an unwanted discharge of a battery as well as improving safety.
Since electric current of an extremely large amount up to several hundred amperes, which flows to the loading side, is passed through the contactor, such large current tends to cause the contactor to be electrically welded at its point of contact. When the contact point is welded, it becomes impossible to cut off output power from the power source even when the ignition switch is turned off. In order to avoid such a difficulty, there have been developed apparatuses for detecting a welded state of the contactor.